Weather rating

Electrial equipment that comes in an enclosure will and enclosures intended for electrical equipment of any kind will be rated based upon the protection that the enclosure can provide against accidental contact and damage from the entrance of water or objects. It is important to check the rating any enclosure being considered to make sure that it is suitable for the location in which the equipment will be installed. There are two different rating systems that are commonly used globally: National Electrical Manufacturers Association (NEMA) rating and Ingress Protection (IP) rating. The two systems are very similar, but it is not possible to create a direct equivalency between the two.

IP rating

A set of standards created by the International Electrotechnical Commission (IEC). Sometimes also referred to as the Ingress Protection Code (IPC). The code may contain other letters and numbers beyond the first two, but these are not relevant for offgrid PV system design and installation. The first character after IP signifies the protection that the enclosure provides against the entrance of foregin bodies and protection of people from hazardous parts. The second character after IP signifies the protection that the enclosure provides against the entrance of moisture.

Example 1: An enclosure is rated IP 65. What level of protection does it offer?

• 6 signifies that it is rated as dust-tight.
• 5 signifies that it is protected against water projected from a nozzle.

IP rating system:
1st letter - protection from solid particles.
2nd letter - protection from liquids.

Code letters	First characteristic numeral: Solid particle protection	Second digit: Liquid ingress protection
IP (Ingress Protection)	Single numeral: 0–6 or letter X	Single numeral: 0–8 or letter X
Mandatory	Mandatory	Mandatory

Solid particle protection

The first digit indicates the degree of protection (of people) from hazardous parts, as well as the protection of enclosed equipment from foreign bodies.

Level sized	Effective against	Description
X	—	X means there is no data available to specify a protection rating with regard to this criterion.
0	—	No protection against contact and ingress of objects
1	50mm	Any large surface of the body, such as the back of a hand, but no protection against deliberate contact with a body part
2	12.5mm	Fingers or similar objects
3	2.5mm	Tools, thick wires, etc.
4	1mm	Most wires, slender screws, large ants etc.
5	Dust protected	Ingress of dust is not entirely prevented, but it must not enter in sufficient quantity to interfere with the satisfactory operation of the equipment.
6	Dust-tight	No ingress of dust; complete protection against contact (dust-tight). A vacuum must be applied. Test duration of up to 8 hours based on airflow.

Liquid ingress protection

The second defines the protection level that the enclosure enjoys from various forms of moisture (drips, sprays, submersion etc).

Level	Protection against
X	X means there is no data available to specify a protection rating with regard to these criteria.
0	No protection against ingress of water
1	Dripping water
2	Dripping water when tilted at 15°
3	Spraying water
4	Splashing of water
5	Water jets
6	Powerful water jets
6K	Powerful water jets with increased pressure
7	Immersion, up to 1m depth
8	Immersion, 1m or more depth
9K	Powerful high-temperature water jets

NEMA rating

The National Equipment Manufacturers Association (NEMA) rating system is primarily used in North America as the national electrical codes mandate that the NEMA rating system is used. The NEMA rating system differs from the IP rating system in that increasing numbers do not signify that the enclosure offers better protection than the number that proceeds it. For example, types 3, 4 and 6 are intended for outdoor use, but type 5 is not. Equipment for offgrid PV systems will fall into ratings 1-5.

Example 1: An enclosure is rated NEMA 3X. What level of protection does it offer and can it be used indoors?

• A NEMA rating of 3 signifies that it is protected against falling dirt and windblown dust, against weather hazards such as rain, sleet and snow, and is undamaged by the formation of ice. A rating of X means that it carries additional protection against corrosion from salt water.
• Its ratings exceed what is needed for indoor installation, therefore it is acceptable to use.

NEMA Type	Definition
1	General-purpose. Protects against dust, light, and indirect splashing but is not dust-tight; primarily prevents contact with live parts; used indoors and under normal atmospheric conditions.
2	Drip-tight. Similar to Type 1 but with addition of drip shields; used where condensation may be severe (as in cooling and laundry rooms).
3	Weather-resistant. Protects against falling dirt and windblown dust, against weather hazards such as rain, sleet and snow, and is undamaged by the formation of ice. Used outdoors on ship docks, in construction work, and in tunnels and subways.
3R	As 3, but omits protection against windblown dust.
3S	As 3, but also operable when laden with ice.
3X, 3RX, 3SX	X indicates additional corrosion protection; commonly used near salt water.
4 and 4X	Watertight. Used outdoors on ship docks, in dairies, in wastewater treatment plants and breweries. X (as 4X) indicates additional corrosion resistance.
5	Dust-tight. Provided with gaskets or equivalent to exclude dust; used in steel mills and cement plants.
6 and 6P	Submersible. Design depends on specified conditions of pressure and time; submersible in water or oil; used in quarries, mines, and manholes. 6 is temporarily submersible, 6P withstands occasional prolonged submersion. Neither are intended for continuous submersion.
7	Certified and labelled for use in locations where specific fire or explosion hazards may exist.
8	Certified and labeled for indoor and outdoor use in locations where specific fire or explosion hazards may exist.
9	Certified and labelled for indoor and outdoor use in locations where specific fire or explosion hazards may exist.
10	Meets specific requires for use in mining applications in the United States.
11	General-purpose. Protects against the corrosive effects of liquids and gases. Meets drip and corrosion-resistance tests.
12 and 12K	General-purpose. Intended for indoor use, provides some protection against dust, falling dirt, and dripping non-corrosive liquids. Meets drip, dust, and rust resistance tests.
13	General-purpose. Primarily used to provide protection against dust, spraying of water and non-corrosive coolants. Meets oil exclusion and rust resistance design tests.